The present invention relates to a technique for recovering and recycling a cured phenolic resin used in a printed board or the like for reuse as a raw material, more specifically to a molded article and a vacuum thermal insulator remolded from the recycled cured phenolic resin and methods for producing the same.
A cured phenolic resin produced by heating and curing a phenolic raw resin can serve as an excellent composite material if used in combination with paper or wood and, therefore, has been used massively in printed boards and building materials. The phenolic resin has been used in combination with paper components (fiber) to form a composite paper-phenolic resin composition.
However, such composite material can become massive wastes when products or articles using such material are junked or when defective goods produced at mass production are junked.
Under such circumstance, an effective technique has been sought for recovering or recycling such composite material from the aspect of resource savings.
In general, since such composite material essentially composed of a thermosetting resin is not molten or fused by heat, it is difficult to recover or recycle it into a raw material. The composite material is refractory to decomposition, which also hinders chemically converting it to a resin raw material or fuel.
This explains the current tendency toward wide use of heat generating when the composite material is burnt.
For effective use of the composite material as a raw material, on the other hand, a proposed method can be found in Japanese Laid-Open Patent Publication No. Hei 6-23751 which pulverizes a waste of a thermoplastic resin together with a waste of a cured resin into a powder and heats the powder under pressure to mold it into a remolded article. The remolded article thus obtained has been applied effectively in components of general use such as house construction material.
However, the above-mentioned conventional method can not solve the current serious demand of resource savings because it fails to show an efficient method for recycling the cured phenolic resin. Furthermore, the above-mentioned prior art gives only a method for reuse of the cured phenolic resin as the component and therefore has a drawback of having a poor additive value of recycling.
In view of the above situation, the present inventors made a vigorous study on the method for recycling such cured phenolic resin and developed an efficient recycling method of the cured phenolic resin preliminarily, which led to a discovery that the cured phenolic resin which may become a massive waste can be recycled and reused as a useful raw material.
More specifically, the object of the present invention is to provide an efficient method for recycling a cured phenolic resin used in a printed board, for example, thereby producing a molded article affording an excellent additive value. Another object of the present invention is to provide a high performance vacuum thermal insulator utilizing the molded article produced by the above-mentioned method.